1. Field of the Invention
This invention relates generally to the manufacture of drill bits of the roller cone type such as are used in the oil and gas producing industry and, in particular, to an improved apparatus and method for rotatably mounting and retaining rock bit roller cones on a drill bit body.
2. Description of the Background
In a typical drill bit of the type having roller cones, there are three major components. These three components include the body of the drill bit, the roller cones, and the bearings which rotatably support the roller cones on the body of the drill bit. The bit body typically includes an uppermost pin for connection to the drill string, a mid portion below the pin which houses the nozzles and pressure compensators, and a plurality (typically three) of legs which depend generally downwardly from the mid portion. A respective roller cone is rotatably mounted on the end of each of these legs.
Although various bearing structures may be employed to rotatably support the roller cones on their respective legs of the body of the drill bit, journal-type bearings are one of the most widely used, the lower or outer portion of each leg of the body of the drill bit being formed into a journal. The roller cone may be rotatably locked onto the journal of its corresponding bit leg by means of a ball bearing system, a locking ring, or other locking device.